Biological production of succinic acid by actinobacillus succinogenes sp. 130Z

Abstract

Physiological and environmental characteristics of succinate-producing Actinobacillus succinogenes sp. 130Z were studied to develop the efficient biological system for succinic acid production. High cell density culture system by external membrane recycle bioreactor was also developed. In high-cell concentration cultivation of Actinobacillus succinogenes, volumetric productivity of succinic acid reached over 6.5 g/L/h. Several factors which affect cell growth and succinic acid production were examined by 100 ml flask and 1L batch cultures. Specific growth rates in the flask cultivation were almost same with increasing glucose concentration up to 40 g/L glucose, but slightly decreased when 80 g/L glucose was used. Cell growth and succinic acid production were also affected by initial pH in flask cultivation. The range between pH 7 and pH 7.5 was the best condition on a view of cell growth and succinic acid production. But the succinic acid yield between pH 6 and pH 6.5 showed higher results than the data between pH 7 and pH 7.5. Other carbon sources including lactose, sucrose, maltose, fructose, mannitol and mannose could be utilized as alternatives to glucose. Among the eight different complex nitrogen sources, only soytone could be utilized for succinic acid production. Magnesium carbonate in the medium could increase succinic acid production. In 1 L batch cultures, volumetric productivity of succinic acid increased when more yeast extract was used. With 60 g/L glucose and 5 g/L yeast extract, cells grew up to $OD_660$ (optical density) of 3.5 and succinic acid productivity reached 0.46 g/L/h. When 60 g/L glucose and 25 g/L yeast extract were used, cell concentration was over $OD_660$ of 9 and succinic acid productivity reached 1.34 g/L/h. Cell concentration and the amount of succinic acid attainable were not dependent on the concentration of phosphorous sources in the medium. Effects of external supply of $H_2$ were examined. The optimum ratio of $H_2/CO_2$ w...